It is known to determine the position of a geostationary satellite by using a system comprising a dedicated station for measuring distance between this station and the satellite, such as a large emitting and receiving TCR (acronym standing for Telemetry Command and Ranging) station, and a specific transponder on board the satellite, included in the TCR subsystem. The distance measurement, obtained by measuring the phase shift induced by the propagation time and the passage through the TCR transponder of the satellite on a sinusoidal or tone ranging radiofrequency carrier and associated with an elimination of ambiguity, is done periodically (weekly, fortnightly or monthly) according to well established procedures. Between the measurement campaigns, the position of the satellite is deduced by orbit determination software. Such a system is costly.
Another solution presented in the U.S. Pat. No. 6,864,838, consists in using a satellite telecommunications system 200 by geostationary satellite SA which comprises, as can be seen in FIG. 1, a station 20 emitting a telecommunications signal 21 of digital video type formatted to the MPEG-2 and DVB-S standards, a telecommunications transponder 22 on board the satellite SA, and a number of stations 23 receiving the telecommunications signal, synchronized with the emitting station so as to have a common time base. The emitting and receiving stations are within the coverage 24 of the satellite SA. The position of the satellite is deduced from the measurement of the propagation time of the signal between the emitting station 20 and a receiving station 23 via the satellite SA. This propagation time is measured by observing known recurrent sequences of bits or unique words of the telecommunications signal 21. When these sequences of bits or unique words are recognized by the receiving station 23, the corresponding reception instant is used with the instant of emission of the start of these sequences of bits and the time base, to compute the propagation time. The knowledge of the geographic position of the broadcasting station 20 and of the receiving stations 23, and the distance measurements making it possible to compute the position of the satellite SA by known mathematical methods such as trilaterisation.
This system works only if the operator of the satellite has access to the telecommunications signal 21 in the broadcasting station 20, either to know the instant of emission to the satellite of unique words pre-existing in the signal, or to insert unique words into the signal at chosen instants. This solution which is included in the satellite telecommunications system, is therefore controlled by a telecommunications operator and/or by a broadcaster and/or by a satellite packager with respect to the telecommunications signal 21 and the broadcasting station 20, and by the satellite operator with respect to the satellite SA and the transponder 22. This solution cannot be used with the telecommunications operator and/or the broadcaster and/or the satellite packager.
Consequently, there still remains a need for a system that simultaneously satisfies all the abovementioned requirements, notably in terms of cost and independence relative to a telecommunications operator.